When S was plucked with the finger the sound was steadily audible
from R'.

When sounds were sung into z of R' the notes were audible from R.

A spring S was fastened to a stretched membrane M + an electro
magnet E fastened over it. Circuit as in Fig 5.
Upon singing into A the sounds were heard from z or R' ­ + upon
singing into z or R' the sounds were audible from A. The word
"papa" uttered into z was intellig-